<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style type="text/css">
		.box {
			position: fixed;
			margin-left: 300px;
			width: 500px;
			height: 500px;
			border: 1px red solid;
		}
		.item{
			position: absolute;
			top: 150px;
			left: 150px;
			width: 200px;
			height: 200px;
			background-color: skyblue;
		}
	</style>
</head>
<body>
<div class="box">
	<div class="item"></div>
</div>
</body>
</html>